It is well known that in many milling operations it is desirable to ensure that the milling force component acting normally on the surface to be milled should be as low as possible, and this in order to avoid phenomena such as strain hardening, which render the milling operation more difficult and which reduce the life of the milling tool. A well known way of ensuring this is to use milling tools wherein the milling cutters present positive axial rake angles, the more positive the angle the greater the reduction of the milling forces acting normally on the milled surface. However, and in practice, as the magnitude of the positive axial rake angle is increased, there comes a stage when the milling force component changes its direction and instead of constituting a force which presses against the milled surface, it is transformed into a force which tends to draw the workpiece being milled from its clamping mechanism and/or to detach the cutting tool from the milling machine quill. The magnitude of the force which acts to detach the workpiece from its clamping mechanism is a function of the magnitude of the positive rake angle, and as this angle increases, so does this detaching force.
It is furthermore well known that the magnitude of these milling forces is directly proportional to the depth of milling effected during each single milling operation. As a consequence, the greater the length of milling contact between the cutting edge and the workpiece, the greater will be the milling forces.
It therefore follows that, in milling operations using milling tools having milling cutters displaying relatively highly positive axial rake angles and wherein the entire length of the cutting edge of the milling cutters is employed in each milling operation, the stability of the workpiece can be deleteriously affected and it is well known that in such cases workpieces tend to be detached from their clamping devices, and that undesirable vibrations, or "chatter", are set up in the milling cutter assembly.
Clearly, these disadvantages could be reduced by ensuring that only a portion of the overall length of the cutting edge of each milling cutter is employed during each single milling operation, but such a solution is clearly disadvantageous when, for example, in carrying out shoulder milling it would necessitate repeated successive milling operations in order to achieve the required depth of milling, and this would not only be burdensome but would, of necessity, give rise to the production of a more or less serrated, milled surface as well as reducing the overall production rate.
It is an object of the present invention to provide a new and improved insert for a milling cutter, particularly for a milling cutter used in face milling operations, wherein the above-referred-to disadvantages are substantially reduced.